"...The Book of Psalms refers to 'those who fear G-d' , which many understand to be a reference to Gentiles who attach themselves to the Jewish faith without converting. G-d's House on Zion's height had a courtyard for Gentiles who wanted to take part."

I am not sure exactly which verse in Psalms he is referring to?

There are many Gentiles who consider themselves proselytes of the Jewish faith, though never formally convert. One was the Noachide scholar Vendyl Jones, who passed away earlier this year. He never made a formal conversion to Judaism, though some of his children did and eventually made aliyah.

He tells a bit about his path to enlightenment as a former Baptist minister in his book here:

It seems to me as if proselyte is an appropriate enough term and I don't understand all this worry and hassle with formal conversions.

13. FOR THE RIGHTEOUS AND PROSELYTES:

May Your compassion be stirred, O Lord our God,
towards the righteous, the pious, the elders of Your people
the house of Israel, the remnant of their scholars, towards proselytes,
and towards us also. Grant a good reward to all who truly trust in Your
name. Set our lot with them forever so that we may never be put to shame,
for we have put our trust in You.
Blessed are You, O Lord, the support and stay of the righteous.http://www.hanefesh.com/edu/amidah.htm